lacunar infarct

**Definition:** Small subcortical infarct (typically 2–15 mm) in the territory of a single penetrating arteriole. Leaves a small fluid-filled cavity ("lacune") on healing. A form of small-vessel disease.

**Pathophysiology:** - Chronic hypertension (the most important risk factor) and diabetes cause lipohyalinosis (segmental arteriolar wall disruption, fibrinoid change, hyaline deposition) and microatheroma of small penetrating arteries (about 200–400 µm). - Less commonly, embolism or larger-vessel atheroma obstructing the origin of a penetrating branch (branch atheromatous disease). - Other risk factors: smoking, age, hyperlipidemia.

**Common locations:** Putamen/lenticular nucleus, posterior limb of the internal capsule, thalamus, caudate, pons (basis pontis), and deep white matter (corona radiata). The vessels involved are the lenticulostriate arteries (MCA), thalamoperforators and thalamogeniculate arteries (PCA), and paramedian pontine branches of the basilar artery.

**Classic lacunar syndromes (no cortical signs: no aphasia, neglect, agnosia, apraxia, or visual field defect; consciousness is preserved):** 1. **Pure motor hemiparesis** (most common): posterior limb of the internal capsule or basis pontis. Contralateral face, arm, and leg weakness with no sensory loss. 2. **Pure sensory stroke:** ventral posterolateral (VPL) thalamus. Contralateral hemisensory loss. 3. **Ataxic hemiparesis:** pons or internal capsule. Ipsilateral weakness plus ataxia, out of proportion to the weakness. 4. **Dysarthria–clumsy hand syndrome:** pons or genu of the internal capsule. Facial weakness, dysarthria, dysphagia, and clumsiness of one hand. 5. **Sensorimotor stroke:** thalamus plus adjacent internal capsule.

**Diagnosis:** - Noncontrast CT first to exclude hemorrhage. CT is often normal early. - MRI with diffusion-weighted imaging (DWI) is the most sensitive test and shows a small hyperintense lesion. Chronic lacunes appear as small CSF-density cavities. - Workup: vascular imaging (carotid/intracranial), ECG/telemetry, lipids, glucose/HbA1c.

**Management:** - Acute: IV thrombolysis (alteplase/tenecteplase) if the patient meets criteria and is within the window, even for mild deficits if disabling. Aspirin is given after hemorrhage is excluded. Short-term dual antiplatelet therapy (aspirin + clopidogrel) may be used for minor stroke or high-risk TIA. - Secondary prevention: BP control (the most important), high-intensity statin, antiplatelet therapy (aspirin, clopidogrel, or aspirin/dipyridamole), glycemic control, smoking cessation.

**Complications and associations:** - Multiple lacunes lead to **vascular dementia** (multi-infarct/subcortical), pseudobulbar palsy, gait disturbance (lacunar state), and emotional lability. - Prognosis for the acute event is generally good, with relatively low early mortality and good recovery, but recurrence risk is significant. - Charcot-Bouchard microaneurysms in the same vessels cause hypertensive **hemorrhage** (putamen is the most common site, followed by thalamus, pons, and cerebellum).

**High-yield boards points:** - HTN → lipohyalinosis → lacunar stroke in the basal ganglia, internal capsule, thalamus, or pons. - Pure motor or pure sensory deficit without cortical signs points to a lacunar stroke. - Gross pathology: small cavitated infarcts (the "lacunes" or "little lakes"). - Contrast: embolic cortical MCA stroke gives aphasia, neglect, or visual field defects. Lacunar strokes do not.